This invention relates to handle bar grips as more particularly directed to said grips having electric heating means provided therein and to the method of manufacturing such grips.
In the operation of unenclosed motor vehicles such as motorcycles and snowmobiles, the operator is exposed to the outside air and is thus subjected to the relative wind generated by the vehicle's movement through the ambient air. At low tempeartures, a severe wind chill effect is encountered, and this can become a serious safety hazard if the operator's hands become so chilled as to inhibit their manipulation of the vehicle and its controls. Since the hands are vital in the control of such vehicles, if they are not kept reasonably warm, extremely dangerous operating failures can result.
Further, since the rider must necessarily grip the handlebars with some considerable pressure, the hands per se are relatively inactive and circulation is restricted. Moreover, while most parts of the body, including the feet, can be protected against cold by the addition of layers of bulky clothing, there is a practical limit to the bulkiness that can be provided in gloves because it is necessary to preserve freedom of movement and "feel" in the hands.
The metal handlebars themselves also constitute a large heat sink which, when cold, rapidly drains heat from the hands.
In any event, since the handlebars control or influence bike balance, steering, clutch, throttle and brake control, it is evident that numb hands caused by the cold present a significant safety problem to the rider.
The problem of providing effective and economical heating means for handle bars grips has been recognized for many years. In U.S. Pat. No. 3,667,315, cartridge heaters are disposed within the handle bars per se. In French Pat. No. 2,254,204, heated handle bar grips are shown, but these involve the use of a separate heating segment adapted to be fitted into a cavity or slot provided within a molded handle bar grip. Swiss Pat. No. 169,903 also discloses heated handle bar grips with electrical heating elements disposed within an extension clamped on the end of a handle bar.
While the above referenced French patent broadly discloses the concept of electrically heated handle bar grips, it fails to disclose a construction therefor to achieve uniform longitudinal and circumferential heating throughout the grip. Moreover, both these prior foreign patents fail to show a heated hand grip construction which readily lends itself to an economical fabrication process. Further, these patents do not teach a hand grip construction for mounting directly onto the handle bars of a vehicle and in which there is minimal transfer of heat to the handle bars, while optimizing the heat transfer to the hands of the vehicle operator.
The principal object of this invention is to provide electrically heated hand grips of improved construction which overcome the drawbacks of the prior art and heretofore available hand grips of this type.
Another object of this invention is to provide electrically heated hand grips having constructional features which lend themselves to a simple and economical manufacturing process.
A further object to this invention is to provide hand grips of the above type in which the heat transfer to the handle bars on which they are fitted is reduced while heat transfer to the hands is optimized.
This invention relates to electrically heated hand grips in which a helically wound electrical resistance heater wire is molded within a synthetic plastic sleeve. The inner and outer surfaces of the sleeve are longitudinally corrugated with alternate ridges and grooves. The grooves on both the inner and outer surfaces of the sleeve have radially coextensive, overlapping circumferential portions at which the sleeve is of minimum wall thickness. The diameter of the heater wire is not less than the minimum wall thickness.